1. Field of the Invention
The present invention relates to an elevator governor for actuating an emergency stop system by detecting an excessive speed of a cage or a counter weight.
2. Description of the Related Art
FIG. 7 shows a construction of a conventional elevator such as disclosed in Japanese Utility Model Laid-Open No. 63-151480. In FIG. 7, a hoist 3 serving as a driving unit is disposed in a machinery room 2 which is located at an upper portion of an elevator passage 1. A plurality of main ropes 4 are wound around a rope sheave 3a on the hoist 3. A cage 5 is connected to one end portion of the main ropes 4 and a counter weight 6 for compensating the weight on the side of the cage 5 is connected to the other end portion of the main ropes 4.
A governor 7 is disposed next to the hoist 3 on the floor of the machinery room 2. An endless governor rope 10 hanging down into the elevator passage 1 is wound around a rope sheave 8 of the governor 7. A tension pulley 9 is suspended at a lower portion of the governor rope 10. Further, the governor rope 10 is connected to a side portion of the cage 5 through an arm 11. Thus, the governor 7 is actuated to slow down or stop the cage 5 when speed of the cage 5 has exceeded a prescribed speed.
A conventional governor will now be described in detail. FIG. 8 is a front view of certain portions showing an example of conventional elevator governors and FIG. 9 is a longitudinal sectional view thereof. In these figures, the sheave 8 having the governor rope 10 wound around thereon is supported on a stand 12 in a manner rotatable about a sheave shaft 13. A pair of flyweights 15 capable of being turned respectively about pins 14 are attached to side surfaces of the sheave 8. The pair of flyweights 15 are linked with each other by means of a link 16.
An actuating piece 15a consisting of a bolt is screwed into one end portion (toward the center of gravity) of each flyweight 15. Each flyweight 15 is turned about the pin 14 such that the respective moving piece 15a is moved radially outward of the sheave 8 due to a centrifugal force resulting from a rotation of the sheave 8. A balancing spring 17 for providing a force against the centrifugal force is provided between the other end portion of one of the flyweights 15 and the sheave 8. A cage stopping switch 19 having an actuating arm 19a which faces the actuating piece 15a is secured on the stand 12 by way of a fixture 18.
A pawl 15b is provided on the other end portion of each flyweight 15. A ratchet 21 is supported as fitted rotatably on a bearing of a bearing portion 12a of the stand 12. Provided on the ratchet 21 are teeth 21a for engaging the pawl 15b only when the sheave 8 is rotated in one particular direction. Further, a rope catch holding hook 22 is provided on the ratchet 21 to hold a rope catch 23.
The operation will now be described. The sheave 8 is rotated as the governor rope 10 travels in synchronization with the going up and down of the cage 5. At this time, the flyweights 15 receive a centrifugal force corresponding to the rotating speed of the sheave 8, i.e., speed of the cage 5 while revolving together with the sheave 8. When speed of the cage 5 has exceeded a predetermined value, the flyweights 15 are turned about the pins 14 against the force of the balancing spring 17.
Further, when the speed of going up and down of the cage 5 has become a first overspeed (normally about 1.3 times the rated speed) which is higher than the predetermined value, the actuating piece 15a abuts the actuating arm 19a of the cage stopping switch 19 due to displacement of the flyweights 15 and turns the actuating arm 19a. Thereby the switch 19 is actuated so that the power of the hoist 3 is cut off and the cage is stopped.
Further, for example when the main ropes 4 are broken, the cage 5 continues to go down without coming to a stop even though the hoist 3 has been stopped. When the cage reaches a second overspeed (normally about 1.4 times the rated speed), the flyweights 15 are furthermore displaced due to a centrifugal force resulting from the rotation of the sheave 8 corresponding to such speed and the pawl 15b is caused to engage the ratchet 21. Since, thereby, the ratchet 21 is rotated in synchronization with the sheave 8 to cause a rotation of the rope catch holding hook 22 provided on the ratchet 21, the engagement between the rope catch holding hook 22 and the rope catch 23 is released. The governor rope 10 is braked by the rope catch 23 and, in a linked connection with this, an emergency stopping system (not shown) provided on the cage 5 is operated to bring the cage 5 to a sudden stop.
FIG. 10 shows a conventional elevator governor such as the one disclosed in Japanese Utility Model Laid-Open No. 54-20465. In FIG. 10, a fixed rope catch 24 is screwed onto the stand 12. Further, a notch 26 is provided in the stand 12 at the lowermost portion in the operating range of a movable rope catch 25.
If the movable rope catch 25 is to be restored after its operation due to the above described second overspeed where it is dropped to the lowermost end portion within its operating range, a rod (not shown) is inserted from the notch 26 provided on the stand 12 to lift the movable rope catch 25.
As disclosed for example in Japanese Patent Publication No. 4-28622, in order to suppress a vibration-like turning of the flyweights 15 in the conventional elevator governor, a spring constant of the balancing spring 17 must be adjusted such that the flyweight 15 starts its turning before reaching the first overspeed of the governor when the rated speed has been exceeded and that the flyweight 15 causes a rotation of the ratchet 21 at a second overspeed. There has been a problem that setting of an operating speed is difficult.
Further, since a gap occurs around the respective pins of the flyweights 15 and the link 16, there has been a problem that the flyweight 15 is shaken up at the time of rotation of the sheave 8 and the detected overspeed is not stable. Furthermore, when causing the rope catch holding hook 22 of the ratchet 11 to hold the rope catch 23, positioning is necessary of the rope catch 23 with respect to the rope catch holding hook 22. There is thus a problem that the restoring operation (holding operation) of the rope catch 23 is complicated and takes time.
Moreover, since it is to be restored from the side of the movable rope catch 25, there has been a problem that a restoring operation of the rope catch 23 is difficult when a gap between the governor 7 and a wall of the machinery room 2 which constitutes a working space and a gap between the governor 7 and the hoist 3 on the opposite side are narrow.